Drive system for bag machine

ABSTRACT

A bag making machine of the type adapted to handle thermoplastic web material and produce side weld bags is provided with a drive system which isolates the inertia of various parts from the common drive motor so as to retain the present accuracy of web registration at the various processing stations, but with a higher production rate of finished bags, or alternatively to provide a wider than usual bag machine, or both. The draw rolls and seal roll are individually driven to minimize the torque demands on the clutch and brake which control development, sealing and severing of the web, and in the disclosed embodiment a Geneva drive is provided for the seal roll.

July 2, 1974 R. J. WECH DRIVE SYSTEM FOR BAG MACHINE 4 Sheets-Sheet 1 Filed March 30, 1972 3,8221 6&

July 2, 1974 R. J. WECH DRIVE SYSTEM FOR BAG MACHINE 4 Sheets-Sheet 3 Filed March 30, 1972 TIG E R. J. WECH DRIVE SYSTEM FOR BAG MACHINE July 2, 1974 4 Sheets-Sheet Filed March 30, 1972 July 2, 1974 R. J. WECH DRIVE SYSTEM FOR BAG MACHINE 4 Sheets-Sheet 4 Filed March 30, 1972 United States Patent 01 :"fice 3,822,168 DRIVE SYSTEM FOR BAG MACHINE Robert .I. Wech, Green Bay, Wis., assignorto FMC Corporation, San Jose, Calif. Filed Mar. 30, 1972, Ser. No. 239,495 Int. Cl. B3Zb 31/00 US. Cl. 156-515 6 Claims ABSTRACT OF THE DISCLOSURE A bag making machine of the type adapted to handle thermoplastic web material and produce side weld bags is provided'with a drive system which isolates the inertia of various parts from the common drive motor so as to retain the present accuracy of web registration at the various processing stations, but with a higher production rate of finished bags, or alternatively to provide a wider than usual bag machine, or both. The draw rolls and seal roll are individually driven to minimize the torque demands on the cutch and brake which control development, sealing and severing of the web, and in the disclosed embodiment a Geneva drive is provided for the seal roll.

BACKGROUND OF THE INVENTION The field of the present invention concerns web handling machines, particularly bag making machines in which a folded thermoplastic web is transversely sealed and severed to produce a stacked output of flat finished bags. In prior-art bag machines of this general type, one limitation on the production rate has been the difficulty of cycling the intermittently driven draw rolls and seal roll sufficiently fast, given certain parameters which are acceptable to the industry; High production rates under present conditions are difficult to achieve in large size bag machines (producing trash bags, for instance) because of limitations relating tothe inertia-of intermittently operated parts, the cycle time with which electric clutchesan d brakes canfloperate, and for various other reasons. Many such machines are operating at ornear the-upper limits of the-drive means, and further production rate increases are' likely'to result iii-at least extraordinary maintenance and attention, if not in unacceptable performance. As machine widths increase, seal roll deflection becomes a problemflncreasing'roll'diameter to resist deflection'increasesthe reflected torque to the clutch drive, resulting in reduced production rates. Subdividing the drive trains into smaller and more responsive individual power sources is one solution, but may not be desirable for the reason that accurate timing control increases in complexity in more or less direct proportion to the number of components.-

SUMMARYOF THE INVENTION I .According to the present invention, a bag machine including intermittently operated components'of relatively high inertia is operated (from a single power source) at 3,822,168 Patented July 2, 1974 wider than usual webs with a machine having its other parts the same size as a conventional machine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 'is a schematic side elevation of a typical bag machine andunwind stand with the path of a web indicated therein by a broken line and arrows.

FIGS. 2-5 are diagrammatic sections illustrating the progressive movement of a web through the web sealing and severing station of the FIG. 1 bag machine.

a FIG. 6 is a'vertical section through the sealing and severing station of the bag machine.

FIG. 7 is a simplified diagrammatic perspective, partly broken away-,flof the drive train of the FIG. 1 bag machine.

FIG. 8 is a fragmentary enlarged horizontal section taken along the lines 88 on FIG. 6.

FIG. 9 is an enlarged horizontal section taken along the lines.99 on FIG. 6.

FIG. 10 is a transverse section taken along the lines 10 10 on FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, the bag machine 20 is associated with an unwind stand 22 which rotatably supports a film roll R. The web W payed out from the roll R may be, for example, J-stock wherein it is longitudinally folded to form two substantially registered panels so that one longitudinal margin of the web is closed and the other longitudinal margin includes two free edges. The web is later transversely sealed and severed so that every two adjacent sealing and severing operations produce one completed side weld bag.

My copending application Ser. No, 760,048, now Pat. 3,663,338, May 16, 1972, discloses a similar bag machine in greater detail, and is assigned to the assignee of the present invention. In certain structural improvements later described, the present invention provides an improved drive system for the components which develop, seal and sever the web into individual bags.

At the inlet end of the machine 20 the web extends past a first set .of infeed rolls 42 connected 'to conventional drive regulating means43. Fromthe infeed rolls, the web is trained around a plurality of idler rollers-44 of a dancer arm assembly 46 and around fixed idler rollers 48. The

, dancer arm assembly 46 functions to accumulate and pay out web in' response to transient values of'web tension,

higher than the presently usual operating speeds, yet with the timing control accuracy necessary for the precise registrationof the web. These improvedresults are obtained by using a Geneva drive train for the sealroll, in conjunction with a common drive motor for the associated draw rolls of the bag machine. The Geneva drive provides amechanical drive connection eliminating the need of a clutch fonthe seal roll, so that the clutch required for the draw rolls is subject to a reduced torque load as compared to previous machines where the clutch handles both the draw rolls and the seal roll. Thus, a bag machine incorporating the improved drive system can either (1) Operate at a'highe'r' than usual speed, or (2') utilize longer or stronger than usual draw and sealjrolls to handlea wider web, or

(3) both operate'at a higher than usual speed and handle I: rolls and also for removing the nip pressure when'rethus tending to maintain the incoming web tension con- Still'ltuThC frame ofthe bag machine 20' includes a base plate 49 having upstanding transversely spaced side frame members 50 adjacent the dancer arm assembly 46, intermediate upstanding side frame members 52 at the midportion of the machine, and side frame members 54 at the discharge end of 'the machine. Between the frame members 50 and 52 is a horizontal accessory platform 56 which mounts hole punching assemblies 58 that punch the web for future handling of the finished bags.

Downstream of the hole punch assemblies 58 an electronic web scanner 60 photoelectrically scans index marks on the web to insure proper registration of the "seal when running printed film. Thus, the scanner 60 is electrically connected to the control circuit of the bag machine to deenergize a clutch and simultaneously energize a brake to arrest movement of the web for the transverse seal and severing operation. After the sealing and severing of the web, the .control circuit is conditioned by a switch to engage the clutch and resume movement of the Web.

quired. Adjacent the draw rolls 74 is a vertically reciproeating sealing bar 78, which cooperates with an intermittently rotating seal roll 80 for transversely sealing and severing the folded web. Reciprocation of the sealing bar 78 is provided by a pair of cams '82 (one of which is shown in FIG. 1) keyed to a main drive shaft 84. As later described in detail, the subject matter of the present invention concerns the drive trains between the drive shaft 84, the draw rolls 74, and the seal roll 80.

Each pair of transverse sealing and severing operations by the sealing bar 78 and the seal roll 80 produces an individual bag which is received by a continuously operating belt conveyor 86. The conveyor 86 comprises a series of transversely spaced and aligned upper and lower sets of belts 88 and 90 respectively, the confronting flights of which grip the bags discharged from the sealing and severing station of the machine to transport them to a stacking table 92. Adjustable guides or stop plates 94 of the stacking table '92 arrange the discharged bags into a stack. Intermediate the belt conveyor 86 and the stacking table 92, the bags pass between conventional corrugating rollers 96 that form temporary longitudinal ribs or corrugations in the bag to resist windage, and through a conventional slow-down mechanism 98 of known construction.

With reference to FIG. 6, the present invention provides an improved drive system in which the draw rolls 74 are isolated from the inertia effects of the seal roll 80, and vice versa, by providing a cog belt and pulley drive train 100 for the draw rolls, and a cog belt and pulley drive train 102 for the seal roll, the end result of which is schematically illustrated in FIGS. 2-5. It is assumed, in order to illustrate complete bags B, that they are longitudinally shortened to correspond in length to only one revolution of the draw rolls 74.

In FIG. 2, the draw rolls 74 have advanced one bag length past the sealing bar 78 and the sealing bar is transversely sealing and severing the web to form the trailing edge of a bag B downstream of the sealing bar, and leading edge of a bag B1 upstream of the sealing bar. At the time of sealing, an assumed index mark 104 on each draw roll and an index mark 106 on the seal roll are about in the 3 oclock positions shown. In FIG. 3, the entrance throat defined by the belts 88 and 90, which operate at relatively high speed, is momentarily closed to strip the trailing edge of the bag B from the seal roll, and transport it to the stacking station. Immediately following, the seal roll 80 begins to rotate, as is also shown in FIG. 3, while the draw rolls remain in the FIG. 2 position, as shown by the index marks. This rotation strips the leading edge of the bag B1 from the seal roll, if molten plastic resulting from the sealing and severing operation left any part of the edge adhered to the seal roll.

FIG. 4 shows the bag B1 about three-fourths developed or advanced by the draw rolls 74, with the next sealing and severing operation to occur along a transverse line at 108 to complete the bag B1 and also form the leading edge of the next bag B2. In this position the seal roll has completed its index while the draw rolls 74 must rotate further, as shown in FIG. 5, until the rolls reach the position shown in FIG. 2. At about the time the line 108 reaches the sealing position, the Sealing bar 78 is ready to close as shown in FIG. 2.

FIG. 6 illustrates further details of the conventional and known construction of the mechanism associated with the draw rolls 74, the sealing bar 78 and the seal roll 80. The web W is guided into the draw rolls 74 by a plurality of stripper fingers 110, the upper set of stripper fingers being carried by a pivot arm 112 (at each side of the machine) that is pivoted to the frame plate 52 by a bolt 114. The cylinders 76 for regulating the nip pressure react on the pivot arms, by means not shown, to force the upper draw roll 74 downwardly against the web and the lower draw roll 74, and initially overcome biasing springs which lift the upper draw roll in the absence of fluid pressure 4 in the cylinders 76. A fixed back-up roll 116 supports the lower draw roll 74 to resist flexure thereof.

Heat from the sealing bar 78 is isolated from the upper draw roll 74 by a heat shield 118, and the sealing bar is carried by a vertically reciprocable beam 120, with interposed thin V-shaped metal clips 122. A latch 124 maintains the sealing bar in its illustrated operative position. When its actuating handle 126 is moved to a vertical position, the sealing bar 78 is swung upwardly away from the path of the web in order to thread the web or to have maintenance access to the sealing and severing operation zone.

Vertical reciprocation of the sealing bar 78 is by a camoperated push rod 130 (only one being shown) at each side of the machine. For this purpose, the beam which supports the sealing bar is provided with trunnions held in bearing boxes, neither of which are shown, and each box is affixed to the upper end of one of the push rods 130. Further, the lower end of each push rod is operatively associated with a follower roller 132 that rides on one of the earns 82. Since the cams 82 (FIGS. 1 and 7) are secured to the main driveshaft 84, they cause vertical oscillation of the sealing bar 78 in timed relation with other operating components driven by the same driveshaft '84.

The previously summarized problem to which the present invention is directed is best explained in conjunction with FIGS. 6 and 7. In conventional bag machines of the type disclosed, the main drive shaft 84, or a comparable power shaft, provides harmonic driving motion for both the intermittently operated draw rolls 74 and the seal roll 80, plus various other components, from a single drive motor M. Intermittent motion is obtained from a clutch 166 and brake 176 which engage and disengage at the proper times in the cycles.

, It is apparent that the maximum machine speed (minimum cycle time) or maximum machine width is, among other factors, dependent upon the torque capacity of the clutch. Torque requirements increase due to added inertial loads as machine speed increases, or as machines are built wider. If inertial loads exceed the torque capacity of the clutch, slippage will occur and result in inaccurate bag length or poor repeat accuracy. Installation of a larger electrical clutch is usually not a practical solution to increase machine speed, because of the inherent increased inertial load of the clutch itself, reflected back to the harmonic drive, and also because of the increased flux buildup time required by the larger clutch coil. Further complications result from seal roll vibration at high speed, and seal roll deflection as machine width or sealing pressures are increased. This necessitates a larger diameter seal roll to resist vibration and deflection, resulting in a prohibitive increased inertial load on the clutch.

From the foregoing, it is believed evident that for a given size of bag machine, reducing the inertia load on the clutch will (1) Allow it to operate faster by reducing the time required per bag cycle, or (2) allow an increase in the size of various components in order to produce larger bags, or (3) allow both an increase in bag size and an increase in the production rate of finished bags.

Thus, the attainment of these improved results, according to one aspect of the present invention, is to (a) isolate the seal roll drive train from the draw roll drive train and to energize only one drive train via the electric clutch, (b) in the foregoing system provide a positive timing and driving connection for both drive trains from a common power source, and (c) to accomplish the functions set forth while providing a phase difference in the timing of the draw rolls and the seal roll so as to strip the seal roll from the web intermediate the sealing and severing operations.

A preferred manner of accomplishing these objectives is illustrated in FIGS. 6 and 7 in conjunction with certain conventional and known operating components briefly outlined as follows: The motor M is provided with a cog belt and pulley drive connection 140 to the driveshaft 84. Extending through a bulkhead 142, the other end portion of the driveshaft 84 is secured to a plate assembly 144 that has a pivotal eccentric connection at 146 to a crank arm 148. As disclosed in my previously identified copending patent application, the eccentricity of the connection at 146 is adjustable, while the drive is in motion, by means of an adjustable abutment, not shown, whicli strikes and rotates a star wheel 150. The effect of such adjustment varies the throw of the crank arm 148 and controls the amount of .web advanced by the draw rolls 74.

For this purpose, the crank arm 148 is coupled by a pivot pin 152 to a gear segment 154 that is mounted for oscillation on a pivot shaft 156. Meshed with the gear segment 154 is a gear 158. Mounted on the same shaft as the gear 158 is a larger gear 160 which is coupled to a clutch input shaft 162 by a gear 164. Associated with the input shaft 162 is an electrically operated clutch 166. As thus far described, it is evident that continuous rotary motion of the driveshaft '84 reciprocates the crank arm 148 to oscillate the gear segment 154, and thereby oscillate the clutch input shaft 162.

Control means for the clutch 166 includes a cam 170 on the driveshaft 84, and an electrical switch 172 which is opened and closed by the cam. When energized, the clutch 166 transmits power in one direction from the clutch input shaft 162 to a draw roll driveshaft 174, the latter being associated with an electrically operated brake 176 which is also controlled by the switch 172 so that with the clutch in power transmitting condition the brake is off, and vice versa. The cog belt and pulley drive train 100 transmits power from the draw roll driveshaft 174 to the lower draw roll 74 in a direction to advance the web gripped by the upper and lower draw rolls. Thus, forward movement of the crank arm 148 in FIG. 7 develops one bag length of web beyond the draw rolls 74, following which the brake 176 locks the belt drive for the lower draw roll and the clutch is disengaged for free movement of the crank arm 148 to its rearward limit of movement.

In accordance with the present invention, the inertia of the draw rolls, plus the relatively minor inertia of the drive components between the draw rolls and the clutch, is the only load to which the clutch is subjected. This allows the use of a comparatively small clutch unit which can be rapidly'cycled, without slippage, to repeatedly produce accurately developed lengths of bag stock. Consequently, the draw rolls 74 can be operated more rapidly than is presently the case with a bag machine having the same size draw rolls but a clutch which handles both the draw rolls and the seal roll, or the bag machine can employ larger draw rolls and operate at presently acceptable production rates, or a bag machine in accordance with the present invention can both handle larger bags and achieve an improved production rate with draw rolls of less than maximum size.

It is a further feature of the present invention that driving power for the seal roll 80 originates from the driveshaft 84, independent of the draw roll drive train, so as to reduce the clutch load as previously indicated, and also so that the seal roll can be timed to start before the clutch engages to feed the web as described in connection with FIGS. 245. In order to positively start and stop the seal roll with the movement of the web, the drive train for the seal roll may conveniently incorporate a Geneva drive unit 182. Secured to the driveshaft 84 is a gear 184 meshed with a gear 186. The latter gear is mounted on the input shaft i188 of a Geneva driver 190, best shown in FIGS. 6 and 8.

In known manner, the Geneva driver 190 includes a drive roller 192, radially offset from the axis of the shaft 188, and a cylindrical locking segment 194 coaxial with the shaft 188. Respectively cooperating with the drive roller and locking segment are recesses 196 and 198 of a Geneva wheel 200, each group of said recesses being eight in number so that one revolution of the input shaft 188 turns the Geneva wheel one-eighth of a revolution. The input to output ratio of the geneva drive unit 182, however, is not critical and other ratios can be used because it is only the positive incremental drive connection which is required for the output shaft 202 which is connected to the Geneva wheel 200.

The shaft 202 is connected to the cog belt and pulley drive train 102 that is coupled to the seal roll 80. The drive train preferably incorporates pulleys of a size which result in the seal roll being rotated some uneven multiple per revolution of the Geneva Wheel so that the same areas of the seal roll do not continuously align with the sealing bar 78 and cause excessive wear of the conventional Teflon outer sleeve on the seal roll.

By nature of its design, the Geneva drive unit 182 does not index for a full 180 degrees of rotation of the input shaft 188, and for the eight-increment Geneva wheel 202, produces an index period during degrees of one complete rotation of the input shaft 188.

In operation, the particular eight-increment Geneva wheel disclosed may be timed to start rotating about 10 degrees before the draw rolls 74 start to feed the web, or at 350 degrees of the machine cycle. This strips the web from the sea roll before the draw rolls start to rotate from 0 degrees. The seal roll '80 rotates simultaneously 'with the draw rolls 74, although at a different velocity, through 125 degrees of the machine cycle, completing its index movement. By this time the web W is under control of the delivery equipment, in this case the conveyor 86, while the draw rolls 74 complete the web feeding process at degrees of the machine cycle. It will be evident that the indexing period can be increased or decreased by providing a Geneva wheel having a larger or smaller number of driving slots, respectively.

The conventional motor M (FIG. 7) is the power source of a cog belt and pulley drive connection 206 for a camshaft 208. A face cam 210 on the camshaft reciprocates a linkage 212 for opening and closing the entrance throat of the belt conveyor 86. Camshaft 208 also has a belt and pulley drive 214 for the bag slowdown mechanism 98 (FIG. 1). Belts 88 and 90 receive power from another motor, not shown.

A further feature of the present invention is illustrated in FIGS. 9 and 10, and concerns provisions for easily removing and then replacing or reinstalling the seal roll 80 in accurate alignment with its cooperating sealing bar 78 without affecting its drive means. Thus, each of the side plates 52 is provided with a milled slot 220 which is precisely located longitudinally of the bag machine. Each slot receives a complementary key 222 which is formed on a flanged bracket 224 which includes a stub s h aft 226. Bolts 225 extend through the side plates 52 into the flanges 227 of the brackets 224.

Opposite the driving end of the seal roll 80, the stub shaft 226 is seated in a bearing 228 that is secured to the seal roll. The other end of the seal roll 80 is provided with a projecting stub shaft 230 and the adjacent stub shaft 232 is seated in a bearing 228 which is secured in a hollow pulley assembly 234 that is part of the drive connection between the seal roll 80 and the Geneva output shaft 202 (FIG. 7).

That part of the pulley assembly which receives the seal roll stub shaft 230 is split to provide a separable clamping segment 236 (FIG. 10), and bolts or screws 238 extend through the clamping segment and into a main body portion 240 of the pulley assembly 234 so as to drivingly grip the seal roll stub shaft 230. Removal of the seal roll '80 is carried out by simply pivoting the sealing bar 78 (FIG. 6) out of the way by vertically positioning the handle 126, removing the clamp bolts 23-8 and the clamping segment 236, and removing the bolts 225 at the opposite end of the seal roll. The seal roll can then be lifted free, but the pulley assembly 234- for driving the seal roll is undisturbed.

From the preceding description, it is believed evident that the present invention provides an improved drive train for a bag machine having intermittently operated draw and sealing rolls by reducing the inertia load on the drive for the rolls, and that while the Geneva drive is a convenient and highly eflicient manner of effecting this result, there are various other ways of accomplishing similar results. By means of the disclosed drive system, larger (and heavier) seal rolls can be employed-in contrast to a conventional machine in which the draw and seal rolls share a common driveshaftand the drive system provides a relatively inexpensive solution to the problem of improved production rates.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is re garded to be the subject matter of the invention.

What is claimed is:

1. In a thermoplastic bag machine including intermittently operated draw rolls for advancing a folded web to a heated sealing bar for consolidating the plies; and intermittently operated seal roll for supporting the web during engagement of the sealing bar therewith; and a drive motor for the draw rolls and seal roll; the improvement comprising a clutch-brake controlled drive train coupling said motor and said draw rolls, and a Geneva drive train coupled to said motor and said seal roll, said Geneva drive train being timed to begin rotation of said seal roll slightly before said clutch-brake begins rotation of said draw rolls.

2. A thermoplastic bag machine comprising a sealing station including a reciprocable sealing bar, draw rolls for intermittently advancing a web to said sealing station, an intermittently rotated seal roll cooperating with said sealing bar during the periodic sealing of the web intermediate said sealing bar and said seal roll, a common drive mechanism for said seal and draw rolls including a drive motor, a main driveshaft coupled to said drive motor for continuous rotation when said motor is energized, a clutch having input and output shafts, means for rotatively reciprocating said input shaft from said main driveshaft, control means operated by said main driveshaft for energizing the clutch for one-direction motion of said output shaft, means coupling said draw rolls to said output shaft, a Geneva driver coupled to said main driveshaft, a Geneva wheel incrementally rotated by said Geneva driver, and means coupling said Geneva wheel to said seal roll.

3. In a bag machine of the type including intermittently operable draw rolls for feeding successive web increments to a heated seal bar cooperable with an intermittently rotatable seal roll providing a web supporting surface for the seal bar which bar makes momentary pressure contact with the seal roll to sever and seal the web during periods of repose, said machine including normally continuously driven shaft means, clutch-brake shaft means, means driven by said shaft means for oscillating said clutchbrake shaft means, means connected to said clutch-brake shaft means for intermittently driving said draw rolls, and means for intermittently driving said seal roll in synchronism with said draw rolls; the improvement wherein said seal roll drive comprises a separate device having an input driven by said normally continuously driven'shaft means and an output that provides intermittent rotary motion, means for connecting the output of said device to said seal roll, said device being timed relative to the operation of said draw rolls so that after the web is sealed and severed, rotation of said seal roll begins slightly before the next rotation of said draw rolls, to free the leading edge of the web from said seal roll before advance of the web by said draw rolls.

4. In a bag machine of the type including intermittently operable draw rolls for feeding successive web increments to a heated seal bar cooperable with an intermittently rotatable seal roll providing a web supporting surface for the seal bar which makes momentary presure contact with the real roll to sever and seal the web during periods of repose, said machine including a common drive mechanism including normally continuously rotatable shaft means for synchronously operating the draw rolls, the seal roll and the seal bar and including a shaft associated with a sequentially operable clutch-brake drivingly connected to said draw rolls for effecting intermittent rotation thereof, and means for driving said seal roll in synchronism with said draw rolls; the improvement wherein said seal roll drive means comprises mechanical drive means deriving an input from said continuously rotating shaft means and converting rotary motion to intermittent motion for driving the seal roll, said drive means including a Geneva-stop motion to provide positive incremental dwell and drive motion for said seal roll.

5. Apparatus according to claim 4 wherein said Geneva-stop motion includes a Geneva wheel and a Geneva driver, said Geneva wheel having an indexing motion period of approximately degrees per 360 degrees of rotation of said Geneva driver.

6. Apparatus according to claim 5, wherein said Geneva driver is timed to begin indexing said Geneva wheel approximately 10 degrees before said draw rolls rotate in order to free the web from said seal roll before said draw rolls further advance the Web.

References Cited UNITED STATES PATENTS 3,524,783 8/1970 Sutherland 156-251 3,730,810 5/1973 Klein 156-510 3,451,870 6/1969 Pearson 156515 3,527,633 9/1970 Bertoglio 156-510 3,558,400 1/1971 Horvath et a1. 1565l0 DOUGLAS 1. DRUMMOND, Primary Examiner U.S. C1. X.R. 156-583 

